in the tense final standoff, dzhokhar tsarnaev was hidden in a bo a boat parked in the watertown driveway of a resident covered by a tarp. a helicopter overhead was able to take what they call thermal images showing the movements inside that boat. joining us now is tom foreman, national security analyst, tom fuentes as well, assistant former director of the fbi. these thermal images, walk us through, tom, what was going on. >> we were just talking about this a moment ago, wolf, astonishing this is the boat here, so you have a sense what we are talking about, nearby house, fence on this side. tom, you were saying in this picture, you can't see much in terms of anybody inside the boat, this picture is still very valuable. why? >> it is going to help you position your tactical people, your observers, sniper observers, bomb techs and any other things. this is being shot in video. we are only seeing the still picture. so, this is getting collected through the -- excuse me, a forward-looking infrared image willing system of the helicopter that system is then being beamed down to a tactical comm